LAUSR

INTRODUCTION Barriers to sustainable virologic suppression (VS) of HIV infected adolescents and young adults include drug resistance mutations (DRMs) and limited treatment options which may impact the outcome of 2nd line antiretroviral therapy (ART). METHODS We sequenced plasma viral RNA from 74 adolescents and young adults (16-24 years) failing 1st line ART at Newlands Clinic, Zimbabwe between October 2015 and December 2016. We evaluated 1st line nucleoside reverse transcriptase inhibitor (NRTI) susceptibility scores to 1st and 2nd line regimens. Boosted PI based ART was provided and viral load (VL) monitored for ≥ 48 weeks. Fisher's exact test was used to evaluate factors associated with VS on 2nd line regimens, defined as VL < 1000 copies/ml (VS1000) or < 50 copies/ml (VS50). RESULTS The 74 participants on 1st line ART had a median (IQR) age of 18 (16-21) years and 42 (57%) were female. The mean (±SD) duration on ART was 5.5 (±3.06) years and the median (IQR) log 10 VL was 4.26 (3.78 - 4.83) copies/ml. After switching to a 2nd line PI regimen, 88% suppressed to < 1000 copies/ml and 76% to < 50 copies/ml at ≥ 48 weeks. A new NRTI was associated with increased VS50 (p=0.031). CONCLUSIONS These 74 adolescents and young adults failing 1st line ART demonstrated high levels (97%) of DRMs despite enhanced adherence counseling. Switching to new NRTIs in 2nd line improved VS. With the widespread adoption of generic dolutegravir, lamivudine and tenofovir combinations in Africa, genotyping to determine NRTI susceptibility may be warranted.